The present invention relates to a self-piercing rivet fastening device, and more particularly to a self-piercing rivet fastening device that can prevent self-piercing rivet dry-firing.
One example of a self-piercing rivet fastening device is described in JP 2007-530287, Gazette (Patent Literature 1). A self-piercing rivet comprises a flange-shaped head and a hollow tubular leg that extends downward from the head. When this rivet is driven into a plurality of members being fastened, such as two panels or the like, for example, the leg perforates the panels, and, while that is occurring, the leg deforms so that the tip thereof expands, whereupon the plurality of members being fastened is joined together by the deformed and expanded leg and the head. Self-piercing rivets are suitable for joining aluminum bodies which are not amenable to welding, and, in view of the fact that aluminum bodies are being adopted for automobile bodies as lighter weights are now being sought, the demand therefor is expected to grow.
The self-piercing rivet fastening device cited in Patent Literature 1 has a C-shaped frame, a punch disposed at one end of the C-shaped frame, and a die disposed at the other end so as to be opposed to the punch. At the one end of the C-shaped frame, a receiver is disposed for accepting self-piercing rivets fed from the self-piercing rivet feeder, and a feeder tube extending from the feeder is connected to the receiver. The punch is attached so as to drive in, toward the die, a self-piercing rivet sent to a driving chamber in the receiver. A self-piercing rivet driven in by the punch is driven into a plurality of members being fastened, those being disposed between the punch and the die, while perforating those members, whereupon the plurality of members being fastened is fastened together.
Patent Literature 1: PCT (WO) 2007-530287, Gazette
Patent Literature 2: TOKKAI [Unexamined Patent Application] No. H6-039650
In the self-piercing rivet fastening device of Patent Literature 1, sensors (281, 283) for detecting the presence of a self-piercing rivet are provided in the feeder tube between the feeder and the receiver. These sensors are supposed to prevent dry-firing by the punch when there is no self-piercing rivet in the receiver. This detection of the presence of a self-piercing rivet is desirable because it prevents punch dry-firing, but is to detect the presence of a self-piercing rivet inside the feeder tube, and is not to detect the presence of a self-piercing rivet that has arrived in the driving chamber of the receiver. Wherefore, there is room for improvement in the self-piercing rivet fastening device of Patent Literature 1 from the perspective of preventing punch dry-firing.
Patent Literature 2 describes a self-piercing rivet fastening device wherein the presence of members being fastened is detected and whereby, when there is no member being fastened between the punch and the die, self-piercing rivet driving is prevented. In Patent Literature 2, there is no description of any detection of the presence of a self-piercing rivet in the receiver.